1. Field of the Invention
The present invention is directed to using a U-shaped slider assembly formed of slippery urethane plastic for engaging a cylindrical stub shaft of a control linkage.
2. Description of the Prior Art
In operating a work vehicle, such as a loader backhoe, the operator controls a plurality of work operations through manipulating various control levers that control the positioning of hydraulic control valves. The hydraulic control valves in turn regulate the flow of hydraulic fluid to hydraulic cylinders that manipulate the work implement. When operating the backhoe the operator turns his seat to face rearwardly. The operator uses control levers to manipulate the boom relative to the tractor, the dipperstick relative to the boom and the bucket relative to the dipperstick.
On some loader backhoes the operator controls the backhoe by operating two control levers. In this control configuration, fore-and-aft movement of the left hand control lever lowers and raises the boom. Side-to-side movement of the left hand control lever moves the boom side-to-side. Fore-and-aft movement of the right hand control lever pivots the dipperstick relative to the boom. Side-to-side movement of the right hand control lever curls and uncurls the bucket relative to the dipperstick.
The control levers extend upwardly through a control console located in the rear of the operators cab. The control levers are operatively coupled to a control linkage that manipulates hydraulic control valves in response to movement of the control lever. In the above described control configuration, each control lever controls two hydraulic control valves. Each hydraulic control lever controls one backhoe function by extending and retracting the appropriate hydraulic cylinder or cylinders. To prevent cross talk between the functions, it is necessary to prevent the operator from twisting the control lever. To that end the control linkages have been provided with elongated slots in which a stub shaft is provided. The elongated slots have side walls that restraining the twisting motion of the control lever. To provide smooth operation, cylindrical bushings formed of anti-friction material such as ultra high molecular weight polyethylene are mounted to the stub shaft and contact the side walls of the elongated slot. The side walls of the elongated slot have sharp edges that can cut and damage the anti-friction bushings.
The control console is provided with control apertures through which the control levers pass. These apertures are larger than the diameter of the control lever to allow for pivotal movement of the control lever. The control aperture may be covered by a rubber boot that engages the control lever and the edge of the control aperture. In another application steel discs can be welded to the control levers. These discs are designed to be located below the control apertures. However they are not in contact with the interior wall of the console and dust and debris may fall onto the control linkages.
A control lever for a work vehicle having a work implement is provided with a vertically extending shaft that operates a control linkage. The control linkage defines a horizontal control plane that is substantially perpendicular to the shaft. The shaft and control linkage control two functions of the work implement by manipulating two hydraulic control valves. The shaft can be moved in two orthogonal directions or arcs. To prevent cross talk between the control functions the control lever is prevented from twisting by a stub shaft that is received in an elongated slot. The side walls of the elongated slot restrain the twisting movement of the control lever. The elongated slot is provided with a U-shaped slider made of an anti-friction material such as slippery urethane plastic. The U-shaped slider has legs that conform to the side walls of the elongated slot. That portion of the stub shaft located in the elongated slot has a cylindrical configuration.